growing degree days

Growing Degree Days (GDD)- are an attempt to quantify heat available for vine development during the growing season.
By convention grape degree days are tallied between Apr 1 & Oct 31, and a base temperature of 50°F is used.

daily average ETo

Evapotranspiration (ET) is the loss of water to the atmosphere by the combined processes of evaporation (from soil and plant surfaces) and transpiration (from plant tissues).
It is an indicator of how much water your crops need for healthy growth and productivity. ET from a standardized grass surface is commonly denoted as ETo.